Atmosphere Contents

3. Energy Variation

Eccentricity of the Earth's orbit

The amount of solar radiation received by the Earth varies with distance from the sun. The Earth's orbit around the sun changes shape from nearly circular to more obviously ellipsoidal. Formally, the change in shape of the orbit is defined in terms of a change in the eccentricity of the ellipse, where:

Eccentricity = (1- b2 / a2)(1/2) 

where,
a is half of the maximum dimension (or length) of the ellipse, and
b is half of the minimum dimension (or width) of the ellipse

Energy variation

In long, thin ellipses, a > b and the eccentricity of the ellipse tends to one. When the ellipse is near circular, a ˜ b, the eccentricity tends to zero.

What is the shape of the Earth's orbit around the sun?